Production steps of a semiconductor substrate include a step of cutting (or slicing) of an ingot into plates. One of methods for cutting an ingot into plates is to cut an ingot by means of a running wire array (multi-wire saw). For example, Patent Document 1 discloses a method of cutting a silicon ingot by means of a multi-wire saw. Patent Document 2 discloses a method of cutting an ingot of a III-V compound semiconductor such as GaAs, InP, or GaSb by means of the multi-wire saw. Patent Document 3 describes cutting an ingot of a III-nitride such as GaN by means of the multi-wire saw.    Patent Document 1: Japanese Patent Application Laid-Open No. 2001-1335    Patent Document 2: Japanese Patent No. 2842307    Patent Document 3: Published Japanese translation of PCT Application No. 2003-527296